Current collectors for vehicles powered from overhead wires have evolved over many years with various improvements to overcome problems involving ease of use, maintenance of electrical contact between the current collecting shoe and the overhead conductor and handling of the stresses imposed on the system under various operating conditions.
As the speed requirements of the electrically powered vehicle increase, vibration and noise problems have become more severe, and the devices which were useful under operating circumstances of some years ago are no longer satisfactory. An important factor is the fundamental condition that the electrical conductor is not rigid. Rather, it is a wire, or a set of wires, which can flex and move within certain limits. Although the wire is braced and restrained in various ways, it can nevertheless oscillate and undergo complex sets of vibrations and other movements.
Thus, although there have been many prior efforts at vibration solutions including springs and other mechanical devices, they have not been entirely satisfactory. Some are too complex and expensive some are simply too difficult to maintain in order to be practical in the field. Examples can be found in the following documents.
______________________________________ Vollmuth 1,448,474 Seidl et al .sup. 4,205,736 Larsson 2,044,886 Bautz .sup. 4,225,023 Larsson 2,426,150 German OS 2,753,932 Delachaux 2,480,912 German OS 2,752,992 Adler et al 4,116,312 ______________________________________